A new class of Scots pine antimicrobial proteins, which act by binding β-glucan

摘要

Scots pine (Pinus sylvestris) produces several small, highly homologous, disulfide-rich proteins (Sp-AMPs) in response to fungal pathogenic attacks. We report here the expression, structure and function of these proteins. One of the Sp-AMPs was cloned into and over-expressed in Pichia pastoris. The purified protein shows antifungal activity against Heterobasidion annosum, causing morphological changes in spores and hyphae. Binding studies revealed that it binds to soluble and insoluble β-(1,3)-glucans, major components of the fungal cell wall, with high affinity. Homology modeling studies suggest a Greek-key-β-barrel fold having a conserved patch on the surface that can accommodate at least 4 sugar units. We conclude that these proteins represent a new class of antimicrobial proteins that can be classified as pathogenesis related (PR) protein family 18.